Apparatus and method for transmitting device to device communication channel in wireless communication system

ABSTRACT

Disclosed is a method and apparatus for processing an initialization for a D2D communication between user equipments (UEs). The method includes: determining D2D subframes available for a D2D communication, the D2D subframes including a first D2D subframe and a second D2D subframe, each of the first D2D subframe and the second D2D subframe including a D2D slot corresponding to D2D slot number 0; and at a start of the D2D slot of the first D2D subframe and at a start of the D2D slot of the second D2D subframe, processing an initialization associated with a pseudo-random sequence of a D2D communication. The first D2D subframe and the second D2D subframe each include a D2D slot corresponding to D2D slot number 1. At least one of the first D2D subframe and the second D2D subframe corresponds to a non-zero subframe number of a radio frame.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation Application of U.S. patentapplication Ser. No. 14/701,429 filed on Apr. 30, 2015, which claimspriority to Korean Patent Application Nos. 10-2014-0154807 filed on Nov.7, 2014 and 10-2014-0161232 filed on Nov. 18, 2014, which are all herebyincorporated by reference in their entirety.

BACKGROUND

1. Field

Exemplary embodiments relate to a wireless communication, moreparticularly, to an apparatus and method for transmitting acommunication channel between terminals in a wireless communicationsystem.

2. Discussion of the Background

An amount of data transmitted through wireless communication hasgradually increased. However, the frequency resources that serviceproviders can provide are limited and have become increasinglysaturated, and thus, mobile carriers continuously develop technologiesfor discovering new frequencies and improving efficient use offrequencies. One of the actively studied technologies to ease thefrequency resource shortage and to create a new mobile communicationservice is Device-to-Device (D2D) communication technology.Representatively, the 3rd Generation Partnership Project (3GPP), whichis a mobile communication standardization association, actively conductsD2D communication technology standardization that is referred to asProximity-based services (ProSe).

The D2D communication includes a communication between terminals, e.g.,user equipments (UEs), located in proximity to each other, such that theterminals can directly send and receive data therebetween using thefrequency band of, or out of the frequency band of, a wirelesscommunication system using a communication technology of the wirelesscommunication system without passing through the infrastructure of abase station, such as an evolved NodeB (eNodeB). This technology enablesa UE to utilize a wireless communication when located out of the area inwhich wireless communication infrastructure is deployed, and provides anadvantage of reducing network load in the wireless communication system.

Because the resources for D2D communication are limited, it may benecessary to exploit the limited resources effectively in performingwireless communications. For example, a communication problem may occurif a UE carrying out a D2D communication processes a baseband signal byusing only existing parameters of the wireless communication system,such as parameters of LTE or LTE-Advanced system parameters, withoutusing one or more parameters configured in consideration of the limitedresource characteristics of the D2D communication.

SUMMARY

One or more exemplary embodiments provide a method and apparatus fortransmitting a Device to Device (D2D) communication signal through a D2Dcommunication channel in a wireless communication system.

One or more exemplary embodiments provide a method and apparatus forgenerating a pseudo random sequence for a D2D communication in awireless communication system. One or more exemplary embodiments providea method and apparatus for providing a scrambling, a frequency hopping,and a group hopping for a D2D communication in a wireless communicationsystem.

One or more exemplary embodiments provide a method of processing aninitialization for a device-to-device (D2D) communication between userequipments (UEs), the method including: determining D2D subframesavailable for a D2D communication, the D2D subframes including a firstD2D subframe and a second D2D subframe, each of the first D2D subframeand the second D2D subframe including a D2D slot corresponding to D2Dslot number 0; and at a start of the D2D slot of the first D2D subframeand at a start of the D2D slot of the second D2D subframe, processing aninitialization associated with a pseudo-random sequence of a D2Dcommunication. Each of the first D2D subframe and the second D2Dsubframe further includes a D2D slot corresponding to D2D slot number 1.At least one of the first D2D subframe and the second D2D subframecorresponds to a non-zero subframe number of a radio frame.

One or more exemplary embodiments provide a user equipment (UE) toprocess an initialization for a device-to-device (D2D) communicationwith another UE, the UE including: a processor configured to determineD2D subframes available for a D2D communication, the D2D subframesincluding a first D2D subframe and a second D2D subframe, each of thefirst D2D subframe and the second D2D subframe including a D2D slotcorresponding to D2D slot number 0, and at a start of the D2D slot ofthe first D2D subframe and at a start of the D2D slot of the second D2Dsubframe, configured to process an initialization associated with apseudo-random sequence of a D2D communication; and a radio frequencysignal transmitter to transceive a D2D signal associated with thepseudo-random sequence. Each of the first D2D subframe and the secondD2D subframe further includes a D2D slot corresponding to D2D slotnumber 1. At least one of the first D2D subframe and the second D2Dsubframe corresponds to a non-zero subframe number of a radio frame.

One or more exemplary embodiments provide a method of processing aninitialization for a device-to-device (D2D) communication between userequipments (UEs), the method including: indexing at least one of a D2Dslot and a D2D subframe available for a D2D communication, the D2Dsubframe being included in a radio frame and including the D2D slot, theradio frame including at least one non-D2D subframe unavailable for aD2D communication; determining at least one of a D2D slot numberassociated with the D2D slot and a D2D subframe number associated withthe D2D subframe, based on a modulo operation; and determining aninitialization associated with a pseudo-random sequence of a D2Dcommunication, the initialization being associated with the D2D slot orthe D2D subframe. The at least one of the D2D slot and the D2D subframehas a non-zero index. The at least one of the D2D slot number associatedwith the D2D slot and the D2D subframe number associated with the D2Dsubframe is zero.

According to one or more exemplary embodiments, by defining an initialvalue of a pseudo-random sequence adaptive for a D2D communication andthe determination time of the initial value, a transmitting UE mayeffectively configure a pseudo-random sequence for scrambling, frequencyhopping and/or group hopping in accordance with D2D resourceconfigurations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a network architecture of a wirelesscommunication system, according to one or more exemplary embodiments.

FIG. 2 is a diagram illustrating a concept of cellular network-basedDevice-to-Device (D2D) communication, according to one or more exemplaryembodiments.

FIG. 3 is a diagram illustrating a concept of a slot in a D2Dcommunication and a resource pool utilized in the D2D communication,according to one or more exemplary embodiments.

FIG. 4 is a diagram illustrating a subframe structure of D2DSS,according to one or more exemplary embodiments.

FIG. 5 is a flowchart illustrating an example of a method oftransmitting a D2D communication signal through a D2D communicationchannel, according to one or more exemplary embodiments.

FIG. 6 is a diagram illustrating an example of a UE to transmit a D2Dcommunication signal through a D2D communication channel, according toone or more exemplary embodiments.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Exemplary embodiments will be described more fully hereinafter withreference to the accompanying drawings, in which exemplary embodimentsof inventive concept are shown. Throughout the drawings and the detaileddescription, unless otherwise described, the same drawing referencenumerals are understood to refer to the same elements, features, andstructures. In describing the exemplary embodiments, detaileddescription on known configurations or functions may be omitted forclarity and conciseness.

Further, the terms, such as first, second, A, B, (a), (b), and the likemay be used herein to describe elements in the description herein. Theterms are used to distinguish one element from another element. Thus,the terms do not limit the element, an arrangement order, a sequence orthe like. It will be understood that when an element is referred to asbeing “on”, “connected to” or “coupled to” another element, it can bedirectly on, connected or coupled to the other element or interveningelements may be present. The present specification provides descriptionsin association with a wireless communication network, and tasks executedin the wireless communication network may be performed in the processwhere a system (for example, a base station) that manages thecorresponding wireless communication network controls the network andtransmits data, or may be performed in a User Equipment (UE) that iswireless linked to the corresponding network and capable ofcommunicating with the network system.

The multiple access method applied to a wireless communication systemmay not be limited to certain technical schemes. Various methods andschemes can be used, including CDMA (Code Division Multiple Access),TDMA (Time Division Multiple Access), FDMA (Frequency Division MultipleAccess), OFDMA (Orthogonal Frequency Division Multiple Access), SC-FDMA(Single Carrier-FDMA), OFDM-FDMA, OFDM-TDMA, OFDM-CDMA. For uplinktransmission and downlink transmission, either TDD (Time DivisionDuplex), which uses different time locations for uplink and downlinktransmissions, respectively, or FDD (Frequency Division Duplex), whichuses different frequencies for uplink and downlink transmissions, may beutilized. Further, both the TDD and FDD schemes may be used for uplinkand downlink transmissions between a base station and a UE.

FIG. 1 is a diagram illustrating a network architecture of a wirelesscommunication system, according to one or more exemplary embodiments.

FIG. 1 illustrates the network architecture of an Evolved-UniversalMobile Telecommunications System (E-UMTS), which is an example of awireless communication system. The E-UMTS system may be Evolved-UMTSTerrestrial Radio Access (E-UTRA), Long Term Evolution (LTE), orLTE-advanced (LTE-A). Wireless communication technologies and/orprotocols of a wireless communication system with which UEs communicatemay be configured according to the respective network system. UEs areconfigured to communicate with a base station supporting one or more ofthe network architectures described herein.

A wireless communication system is widely deployed to provide variouscommunication services, such as voice and packet data, etc. Also, awireless communication system may support a device to device (D2D)communication between UEs. A wireless communication system supportingD2D communication will be described later in more detail.

Referring to FIG. 1, an Evolved-UMTS Terrestrial Radio Access Network(E-UTRAN) includes a base station (hereinafter referred to as an evolvedNodeB (eNB) 20) that provides a terminal (hereinafter referred to asUser Equipment (UE) 10) with a Control Plane (CP) and a User Plane (UP).

The UE 10 may be a stationary or mobile entity, and may be referred toas a Mobile station (MS), an Advanced MS (AMS), a User Terminal (UT), aSubscriber Station (SS), a wireless device, or the like.

The eNB 20 may generally refer to a station that communicates with theUE 10, and may be referred to as a Base Station (BS), a Base TransceiverSystem (BTS), an access point, a femto-eNB, a pico-eNB, a Home eNB, arelay, or the like.

The eNB 20 may provide at least one cell to a UE. A cell may refer to ageographical area in which the eNB 20 provides a communication service,or a specific frequency band. A cell may refer to downlink frequencyresource and/or uplink frequency resource. Also a cell may refer to thecombination of downlink frequency resource and optional uplink frequencyresource. Also, if carrier aggregation (CA) is not considered, uplinkand downlink frequency resources generally exist in pairs within a cell.

An interface for transmitting user traffic or control traffic may beused between eNBs 20. A source eNB 21 may refer to an eNB which hasestablished a wireless bearer with a UE 10 currently, and a target eNB22 mar refer to an eNB, which a UE 10 that disconnects a wireless bearerwith a source eNB 21 attempts to handover to and establish a newwireless bearer with.

eNBs 20 may be connected with each other via an X2 interface, which isused to send and receive a message between eNBs 20. An eNB 20 isconnected to an Evolved Packet System (EPS), more specifically MobilityManagement Entity (MME)/Serving Gateway (S-GW) 30, via S1 interface. S1interface supports many-to-many-relation between eNBs 20 and MME/S-GWs30. PDN-GW 40 is utilized to provide packet data service toward MME/S-GW30. PDN-GW 40 varies depending on the purpose of communication orservice, and PDN-GW 40 supporting a specific service can be found usingAccess Point Name (APN) information.

Hereinafter, the term “downlink” refers to a communication from a basestation to a UE, and the term “uplink” refers to a communication from aUE to a base station. For downlink, a transmitter may be part of a basestation, and a receiver may be part of a UE. For uplink, a transmittermay be part of a UE and a receiver may be part of a base station. Thebase station may include an eNB, a relay, and the like as describedabove, for example. There is no limitation in the multiple access methodapplied to a wireless communication system.

The wireless communication system may include a radio protocolarchitecture associated with a user plane and a radio protocolarchitecture associated with a control plane, according to one or moreexemplary embodiments. The user plane indicates a protocol stack foruser data transmission, and the control plane indicates a protocol stackfor control signal transmission.

Physical (PHY) layers of a UE and an eNB provide an information transferservice to a higher layer using a physical channel. A physical (PHY)layer is connected to a Media Access Control layer which is a higherlayer, through a transport channel. Data is transferred, through atransport channel, between the MAC layer and the physical layer. Thetransport channel is classified based on a scheme of transmitting datathrough a radio interface. In addition, data is transferred through aphysical channel between different physical layers (that is, betweenphysical layers of a UE and an eNB, between physical layers of atransmitter and a receiver). The physical channel may be modulated basedon an Orthogonal Frequency Division Multiplexing (OFDM) scheme, and usesa space formed of time and frequencies, and a space formed of aplurality of antennas as radio resources. Hereinafter, examples ofphysical control channels will be described.

A Physical Downlink Control CHannel (PDCCH) among physical channels mayinform a UE of resource allocations of a Paging CHannel (PCH) and aDownLink Shared CHannel (DL-SCH) and Hybrid Automatic Repeat Request(HARQ) information associated with a DL-SCH. A PDCCH may deliver, to aUE, uplink scheduling grant which reports resource allocation of uplinktransmission. A Physical Control Format Indicator CHannel (PCFICH)informs a UE of the number of OFDM symbols used for PDCCHs, and istransmitted in each subframe. A Physical Hybrid ARQ Indicator CHannel(PHICH) carries a HARQ ACK/NACK signal as a response to uplinktransmission. A Physical Uplink Control CHannel (PUCCH) delivers HARQACK/NACK with respect to downlink transmission and uplink controlinformation such as a scheduling request and a Channel Quality Indicator(CQI). A Physical Uplink Shared CHannel (PUSCH) delivers an UpLinkShared CHannel (UL-SCH). The PUSCH may include HARQ ACK/NACK and ChannelState Information (CSI) such as a CQI. Recently, methods for carryingout discovery and direct communication between in-coverage orout-of-coverage devices in a network have been studied for the purposeof public safety, etc. A UE performing D2D communication may be referredas a D2D UE. Further, a UE transmitting a signal based on a D2Dcommunication may be referred to as a transmitting (Tx) UE, and a UEreceiving a signal based on a D2D communication may be referred as areceiving (Rx) UE. A Tx UE may transmit a discovery signal, and an Rx UEmay receive the discovery signal. A Tx UE and an Rx UE may exchangetheir roles therebetween. Further, a signal transmitted by a Tx UE canbe received by two or more Rx UEs. Also, D2D communication between a TxUE and an Rx UE may be called a sidelink, which is distinct fromexisting uplink and downlink between an evolved NodeB and a UE.

Hereinafter, a UE is assumed to support D2D communication. A UEsupporting a D2D communication may carry out a D2D communication if auser of the terminal switches it on (from switched off state) to makethe UE D2D-enabled by manipulating User Interface (UI). Further, a UEmay be operated in a D2D-enabled configuration consistently, inaccordance with the characteristics of the UE (e.g., a terminalmanufactured for public purposes) or subscriber policy (e.g., publicsafety plan, etc.).

Also, network (for example, a D2D server which manages a ProSe(Proximity Services) ID and a ProSe application ID, a serving basestation of a corresponding UE) may determine whether a D2D communicationis granted at a UE in which its user enabled a D2D communication. Morespecifically, the UE may carry out a D2D communication only when a D2Dcommunication is granted by a network even though the UE has beenenabled to use a D2D communication by the user. Information on whetherD2D is granted may be output on a display of the UE.

The resources for a D2D communication may be allocated by a UE, e.g., acluster head, responsible for allocating the resources for a D2Dcommunication or a base station. A UE may need to transmit buffer statusreport (BSR) for D2D data to the base station or the cluster head duringa D2D communication. The base station and the cluster head may bereferred to as a base station collectively for convenience ofdescription.

The load at a base station can be distributed and reduced if adjacentUEs perform D2D communications in a cellular system. Also, when adjacentUEs carry out D2D communications, UE's transmission power consumptionand transmission latency may be reduced because UEs send data to atarget located within a relatively short distance. Moreover, from theperspective the whole system, frequency utilization effectiveness isenhanced because existing cellular-based communication and D2Dcommunication use the same resources.

D2D communication may be classified into a communication method ofin-coverage UE, which is located in network coverage (base stationcoverage) and a communication method of out-of-coverage UE, which islocated out of network coverage. Also, D2D may be referred to asProximity based Service (ProSe) or ProSe-D2D. The usage of the termProSe for D2D is intended not to change the meaning of technologytransceiving data directly between UEs, but to indicate the features ofproximity-based service in addition to the device-to-devicecommunication.

FIG. 2 is a diagram illustrating a concept of cellular network-basedDevice-to-Device (D2D) communication, according to one or more exemplaryembodiments.

Referring to FIG. 2, the communication between a first UE 210 located ina first cell and a second UE 220 located in a second cell may be D2Dcommunication between a UE included in a network coverage and a UEincluded in the network coverage. In addition, the communication betweena third UE 230 located in the first cell and a forth UE 240 located in afirst cluster may be D2D communication between a UE included in anetwork coverage and a UE located outside the network coverage. Thecommunication between the fourth UE 240 located in the first cluster anda fifth UE 250 located in the first cluster may be D2D communicationbetween two UEs located outside the network coverage.

A fifth UE 250 may operate as a Cluster Head (CH) in a first cluster. Acluster head refers to a UE responsible for allocating resources. Thecluster head may include an independent synchronization source (ISS) forsynchronizing out-of-coverage UEs. An ISS is a synchronization sourceother than a base station, which does not induce transmissionsynchronization from other D2D synchronization sources.

In one or more exemplary embodiments, in carrying out a D2Dcommunication, a base station 200 may transmit Downlink ControlInformation (DCI) to a first UE 210, where the Downlink ControlInformation may include control information for indicating D2Dscheduling assignment (SA) information, which will be transmitted fromthe first UE 210 to other D2D UEs. The first UE 210 is a UE locatedwithin the coverage of the base station 200. In a D2D communication froma first UE 210 to other D2D UEs (e.g., a second UE 220), D2D SAinformation may include allocation information about availabletransmission resources and/or reception resource and other controlinformation.

A first UE 210, which received Downlink Control Information includingcontrol information for indicating D2D SA information from base station,may transmit D2D SA information to a second UE 220. The second terminal220 may be a UE located out of the coverage of the base station 220. Thefirst UE 210 and the second UE 220 may perform D2D communication basedon D2D SA information. Specifically, the D2D communication may include:receiving, at the second UE 220, D2D SA information; based on the D2D SAinformation, obtaining information indicating resources in which D2Ddata of the first UE 210 is transmitted; and receiving, from the firstUE 210 to the second UE 220, data via information indicating resourcesin which D2D data of the first UE 210 is transmitted.

Various signals may be used for D2D communication. Some definitions arepresented below, but are not limited as such.

First, as a synchronization signal for D2D communication between UEs(D2DSS), there are Primary D2D Synchronization Signal (PD2DSS) andSecondary D2D Synchronization Signal (SD2DSS). Here the entitytransmitting a synchronization signal refers to D2D SynchronizationSource (D2D SS), and information identifying D2D SS is referred to asPhysical Synchronization Source Identity (PSSID).

D2D SS is a node capable of transmitting D2D synchronization signal,where transmitting D2D (Tx D2D) Synchronization Source is a source fromwhich a UE receives a D2D synchronization signal, and Original D2DSynchronization Source is a source from which a D2D synchronizationsignal is originated.

D2D SS_(ue_net) is a set of D2DSS sequences transmitted from a UE when atransmission timing reference is an eNB, and D2D SS_(ue_oon) is a set ofD2DSS sequences transmitted from a UE when a transmission timingreference is not an eNB.

Next, one of channels in which system information related to D2Dcommunication or information related to synchronization is transmittedincludes Physical D2D Synchronization Channel (PD2DSCH). The examples ofcontrol information transmitted on PD2DSCH are D2D frame number (DFN)and out-of-coverage D2D resource pool, and other control information maybe included in PD2DSCH and indicated.

In a D2D communication, physical layer control information may betransmitted on Physical Sidelink Control Channel (PSCCH). In thisconfiguration, the physical layer control information includesScheduling Assignment (SA) information. Although PSCCH is similar toPUSCH format for Wide Area Network (WAN) communication such as LTE, itcorresponds to ProSe dedicated physical channel for transmittingphysical layer control information. More specifically, although PSCCHformat may be similar to the PUSCH format at least in part, some or allof parameters may be provided as values different from those of aphysical channel for a WAN transmission. Further, actual traffic datadistinguished from physical layer control information in D2Dcommunication may be referred to as the term D2D data.

As described above, since the path for D2D communication may be calledsidelink, the term PD2DSCH may include Physical Sidelink BroadcastChannel (PSBCH). Also PSSID may indicate Physical SidelinkSynchronization Identity as well as Physical Synchronization SourceIdentity.

In a D2D communication, a UE may operate in a first mode and a secondmode. The first mode is a mode in which the UE is capable of carryingout D2D communication only when the UE has been assigned resources for aD2D communication from a base station, where a base station sends a D2Dgrant to a transmitting UE, which transmits a D2D signal to another UE.The D2D grant provides the transmitting UE with parameter informationthat needs to be decided by a base station among pieces of SchedulingAssignment (SA) information that needs to be obtained at a receiving UEfor D2D data reception in a D2D communication, resource allocationinformation for the SA, and resource allocation information for dataindicated by the SA. The parameter information that needs to be decidedby the base station includes resource allocation information for dataindicated by the SA. The D2D grant is forwarded to a transmitting UE inDownlink Control Information (DCI), and may be carried in PhysicalDownlink Control Channel (PDCCH) or Enhanced PDCCH (EPDCCH). The D2Dgrant may be control information with its distinct D2D purpose indicatedby uplink grant or D2D-RNTI assigned to each UE. The D2D grant may bereferred to as SA/data grant.

To begin a D2D communication between UEs in the first mode, D2D resourcepool may need to be defined in advance. D2D resource pool refers to aset of necessary resources for control information related to D2Dcommunication or data transmission and reception, including resourcesfor D2D scheduling assignment (SA) transmission (“resource for receivingD2D SA” from the perspective of D2D receiving UE), resources for D2Ddata transmission and reception, resources for transmitting a discoverysignal (“resources for receiving a discovery signal” from theperspective of D2D receiving UE), etc. Basically, D2D communicationutilizes uplink subframes in which an opportunity for a UE to transmit asignal. Accordingly, in a Frequency Division Duplex (FDD) system, everysubframe can be a candidate for D2D resource pool, and in a TimeDivision Duplex (TDD) system, one or more uplink subframes determinedaccording to TDD UL-DL configuration can be a candidate for D2D resourcepool.

FIG. 3 is a diagram illustrating a concept of resource pool used for D2Dcommunication and a slot in D2D communication, according to one or moreexemplary embodiments.

Referring to FIG. 3, in a LTE frame structure at the top, each frame isassigned system frame number (SFN) 0, 1, . . . , N, where each frameincludes 10 subframes. Each subframe includes 2 slots, where the numberof each slot n_(s) is given 0˜19 in a frame. Also the slot number beginsfrom 0 again once when frame is changed. Here, resources for a UE isallocated in all frames, all subframes, and all slots so that acommunication is available.

In a D2D frame structure at the bottom, the concept of SFN(or DFN (D2Dframe number)) is identical with the frame structure at the top.However, since D2D communication is possible only in a D2D resource poolprepared for D2D communication, the D2D frame structure at the bottom isdifferent from the frame structure at the top where D2D communication ispossible in all frames, all subframes, and all slots.

Hereinafter, subframes included in a D2D resource pool are referred toas D2D subframes, and slots included in a D2D resource pool are referredto as D2D slots. Also, the subframes, which are D2D subframes includedin a D2D resource pool, used for transmitting synchronization signals,Primary D2D Synchronization Signal (PD2DSS) and Secondary D2DSynchronization Signal (SD2DSS), are referred as D2DSS subframes. In aD2DSS subframe, Physical D2D Synchronization Channel (PD2DSCH) is alsotransmitted which will be described later.

Likewise, as a D2D subframe included in the D2D resource pool, asubframe used for transmitting data in a D2D communication may bereferred as D2D data subframe; considering that Physical Sidelink ShareChannel (PSSCH) is a channel used for data transmission in the D2Dcommunication, and the D2D subframe may be referred to as PSSCHsubframe.

Further, as a D2D subframe included in the D2D resource pool, thesubframe used for transmitting control information such as D2D SA, etc.may be referred as D2D SA subframe; considering that Physical SidelinkControl Channel (PSCCH) is the channel used for transmitting controlinformation such as D2D SA, etc., the D2D subframe may be referred to asPSCCH subframe.

Further, as a D2D subframe included in the D2D resource pool, a subframeused for transmitting a D2D discovery signal may be referred as D2Ddiscovery subframe; considering that the channel used for transmittingthe D2D discovery signal is Physical Sidelink Discovery Channel (PSDCH),the D2D subframe may be referred to as PSDCH subframe.

Moreover, PD2DSCH is a channel used for transmitting broadcastinformation in D2D communication, and may be referred to as PhysicalSidelink Broadcast Channel (PSBCH) as described above, and the D2Dsubframe in which PD2DSCH is transmitted may be referred as PSBCHsubframe. Also, since PD2DSCH is also transmitted in D2DSS subframe asstated above, the PSBCH subframe and the D2DSS subframe may be the samesubframe.

For example, a D2DSS subframe may have the structure as shown in FIG. 4,but not limited as such. Referring to FIG. 4, a D2DSS subframe in anormal cyclic prefix (CP) includes total 14 OFDM symbols in a time axisand total 6 physical resource blocks (PRBs) in a frequency axis. Among14 OFDM symbols, OFDM symbols corresponding to OFDM symbol numbers 1, 5,6, 7, 8, 12, 13 are assigned to PD2DSCH, OFDM symbols corresponding toOFDM symbol numbers 2, 9 are assigned to PD2DSS, OFDM symbolscorresponding to OFDM symbol numbers 3, 10 are assigned to SD2DSS, OFDMsymbols corresponding to OFDM symbol numbers 4, 11 are assigned to DMRS,OFDM symbol corresponding to OFDM symbol number 14 is used as guardperiod (GP). The transmission period of D2DSS subframe may be 40 ms.

D2DSS may be transmitted in the D2DSS subframe. D2DSS includes PD2DSSand SD2DSS. As shown in FIG. 4, PD2DSS and SD2DSS may be transmittedusing two symbols, respectively, in the D2DSS subframe. Also as shown inFIG. 4, PD2DSCH may be transmitted in the D2DSS subframe, whereDemodulation Reference Signal (DM-RS) may be transmitted as ademodulation reference signal for PD2DSCH. FIG. 4 is just an example, sothe exact symbol position may be defined differently in a differentposition in the synchronization subframe, except that two symbols areused for PD2DSS and SD2DSS, respectively.

Referring to FIG. 3, in the second mode, D2D slot number is obtained byre-indexing an index value consecutively from 0 to the slots whichbelong to a D2D resource pool and applying a modulo-20 operation on eachindex value. For example, the index values in a D2D resource pool are 0,1, 2, . . . , 18, 19, 20, 21, . . . , and by applying modulo-20operation to each index value, D2D slot numbers 0, 1, 2, . . . , 18, 19,0, 1, . . . are generated. D2D slot numbers are assigned regardless ofSFN or DFN, and all of D2D slot numbers 0˜19 need not to be locatedwithin one frame.

In the first mode, D2D slot number is obtained by assigning,contiguously from 0, index values for the slots belonging to uplinksubframes between scheduling assignment periods and applying modulo-20operation on an index value.

D2D slot number may be represented by n_(s_D2D), but not limited assuch.

Similarly, D2D subframe number may be defined. Regarding D2D subframesas shown in FIG. 3, in the second mode, D2D subframe number is obtainedby re-indexing index values for D2D subframes in a D2D resource poolcontiguously from 0 and applying modulo-10 operation on each indexvalue. For example, where the index value of D2D subframe in a D2Dresource pool is 0, 1, 2, . . . , 8, 9, 10, 11, . . . , application ofmodulo-10 operation to each index value yields D2D subframe numbers 0,1, 2, . . . , 8, 9, 0, 1, . . . . That is, D2D subframe numbers aregiven regardless of SFN or DFN, and all of D2D subframe number 0˜9 arenot necessarily located within one frame. In the first mode, D2Dsubframe number is obtained by assigning, contiguously from 0, indexvalues for the subframes belonging to uplink subframes betweenscheduling assignment periods and applying modulo-10 operation on eachindex value.

D2D subframe number may be expressed as n_(sf_D2D), but not limited assuch. Also, the relationship between D2D slot number and D2D subframenumber can be represented as n_(sf_D2D)=└n_(s_D2D)/2┘. That is, aninteger obtained by rounding down the half of D2D slot number by 2 isD2D subframe number.

As stated above, D2D slot number is a value obtained by re-indexing,contiguously from 0, index values for the slots in a D2D resource pooland applying modulo-20 operation to each of the indexed value. Here, theindexed values just before applying the modulo-20 operation to D2D slotnumber may be defined as ‘D2D slot number before modulo-20 operation’.The D2D slot number before modulo-20 operation may be expressed asn_(ss) which is the number of sidelink slot (ss). Particularly, in casewhere the n_(ss) is for the slots defined on PSSCH, which is a channelused for data transmission in D2D communication, it may be expressed asn_(ss) ^(PSSCH), but is not limited as such.

In accordance with the above definitions described herein, therelationship between n_(s_D2D) and n_(ss) (or n_(ss) ^(PSSCH)) may beexpressed as n_(s_D2D)=(n_(ss))mod 20 (or n_(s_D2D)=(n_(ss) ^(PSSCH))mod20).

As explained in the above, D2D subframe number is a value obtained byre-indexing, contiguously from 0, index values for subframes in a D2Dresource pool and applying modulo-10 operation to each index value.Here, the value just before applying modulo-10 operation to D2D subframenumber may be defined as ‘D2D subframe number before modulo-10operation’. The D2D subframe number before modulo-10 operation may beexpressed as n_(ssf) which is the number of sidelink subframe (ssf), butis not limited as such. Specifically, in case where the n_(ssf) is forthe slots defined on PSSCH which is a channel used for data transmissionin D2D communication, it may be expressed as n_(ssf) ^(PSSCH), but isnot limited as such. Further, the relationship between n_(ss) (or n_(ss)^(PSSCH)) and n_(ssf) (or n_(ssf) ^(PSSCH) ) may be expressed asn_(ss)=└n_(ssf)/2┘ (or n_(ss) ^(PSSCH)=└n_(ssf) ^(PSSCH)/2┘).

In accordance with the definitions presented herein, the relationshipbetween n_(sf_D2D) and n_(ssf) (or n_(ssf) ^(PSSCH)) may be expressed asn_(sf_D2D) (n_(ssf))mod 10 (or n_(sf_D2D) (n_(ssf) ^(PSSCH))mod 10).

FIG. 5 is a flowchart illustrating an example of a method oftransmitting a D2D communication signal through a D2D communicationchannel, according to one or more exemplary embodiments.

Referring to FIG. 5, a UE computes an initial value c_(init) to be usedfor generating pseudo-random sequence c(i) at a determined start point,such as at the start of each D2D subframe (first start points), in eachD2D slot (or at the beginning (or start) of each D2D slot) fulfillingn_(s_D2D)=0 (second start points) and at the start of each D2DSSsubframe (third start points), etc.

According to one or more exemplary embodiments, the first start pointscorrespond to the start of each D2D subframe. Here, when the D2Dsubframe is a PSSCH subframe as described in the above, the start ofeach D2D subframe are referred to as the start of each (or every) PSSCHsubframe.

Further, according to one or more exemplary embodiments, second startpoints correspond to each D2D slot (or at the beginning (or start) ofeach D2D slot) fulfilling n_(s_D2D)=0. Here, as described in the above,the start point of D2D slot corresponding to the slot number of 0 hasthe same meaning as the start point of D2D subframe corresponding to thesubframe number of 0, the start point of D2D slot having a slot number,which corresponds to zero after applying modulo-20 operation, the startpoint of D2D subframe having a subframe number, which corresponds tozero after applying modulo-10 operation.

Accordingly, the start point of D2D slot having slot number 0 may beexpressed as the start point of D2D subframe having subframe number 0.Specifically, the start point of D2D slot having slot number 0 may beexpressed as ‘in each D2D slot (or at the beginning (or start) of eachD2D slot) fulfilling n_(sf_D2D)=0’ and as the same meaning of ‘in eachD2D slot(or at the beginning(or start) of each(or every) D2D slot)fulfilling n_(ss) mod 20=0 (or n_(ss) ^(PSSCH) mod 20=0)’. Further, thestart point of D2D subframe having the subframe number 0 may beexpressed as ‘in each D2D subframe(or at the beginning(or start) ofeach(or every) D2D subframe) fulfilling n_(sf_D2D)=0’ or ‘in each D2Dsubframe(or at the beginning(or start) of each(or every) D2D subframe)fulfilling n_(ssf) mod 10=0 (or n_(ssf) ^(PSSCH) mod 10=0)’.

According to one or more exemplary embodiments, third start pointscorrespond to the start point of each D2DSS subframe. Here, if the D2DSSsubframe is identical to PSBCH subframe as described in the above, thestart point of each D2DSS subframe corresponds to the start point ofeach (or every) PSBCH subframe.

The first start points, second start points, and third start points willbe described in more detail below. With the example of the bottom framestructure in FIG. 3, if it is assumed that D2D subframe number startsfrom 0 in frame with SFN=0, first start points in the frame having framenumber SFN=0 illustrated in the bottom of FIG. 3 include the start pointof D2D subframe #2, the start point of D2D subframe #6, and the startpoint of D2D subframe #8.

For example, the second start points illustrated in the bottom of FIG. 3include the start point of D2D slot having slot number 0 (zero) in aframe with SFN=0 and the start point of D2D slot having slot number 0(zero) in a frame with SFN=N.

A third start point may refer to the start point of a subframe in whichD2DSS is transmitted, and if the period of D2DSS subframe is assumed tobe 40 ms, it can be expressed as in each radio frame (or at thebeginning (or start) of each radio frame) fulfilling (n_(f_D2D))mod 4=A,where n_(f_D2D) indicates a SFN or DFN in D2D and A is one selected fromamong 0, 1, 2 and 3. Here, A can be set to one value (e.g., A=0), orconfigured by higher layer signaling.

Here, the initial value c_(init) may be computed based on the types of aD2D communication channel for which a corresponding pseudo-randomsequence is used, and equation and the start points defined by basebandprocessing.

<D2D Data Transmission Channel>

In an exemplary embodiment, when a UE attempts to transmit D2D data onPhysical Sidelink Share Channel (PSSCH) which is a D2D communicationchannel, the PSCCH may have a format similar to that of Physical UplinkShared Channel (PUSCH) in WAN communication such as LTE, etc.

In this configuration, an initial value c_(init) which is used forscrambling of a codeword on PSSCH is computed at first start points, andthe following equation is used.c _(init)=(SA ID)·2¹⁴ +└n _(S_D2D)/2┘·2⁹+510  [Equation 1]

Equation 1 is derived from the following equation 2 which computes aninitial value c_(init) used for scrambling a codeword on PUSCH bysubstituting SA ID that is an ID included in Scheduling Assignment (SA)for a radio network temporary identifier (RNTI) n_(RNTI), setting theindex of codeword with q as zero, substituting a D2D slot numbern_(s_D2D) for slot number n_(s), and setting N_(ID) ^(CELL) as 510.c _(init) =n _(RNTI)·2¹⁴ +q·2¹³ +└n _(S)/2┘·2⁹ +N _(ID)^(cell)  [Equation 2]

According to an exemplary embodiment, when a UE attempts to transmit D2Ddata on PSSCH which is a D2D communication channel, an initial valuec_(init), which is used for frequency hopping for resource blocksassigned for the transmission of PSSCH, is computed at the second startpoints, and the following equation is used.c_(init)=510  [Equation 3]

Equation 3 is derived from the following equation 4, which computes aninitial value c_(init) used in frequency hopping for resource blockassigned for the transmission of PUSCH, by substituting 0 (in case ofTDD) for SFN n_(f), and setting N_(ID) ^(CELL) as 510.FDD:c_(init)=N_(ID) ^(cell)TDD:c _(init)=2⁹·(n _(f) mod 4)+N _(ID) ^(cell)  [Equation 4]

According to an exemplary embodiment, when a UE attempts to transmit D2Ddata on PSSCH which is a D2D communication channel, an initial valuec_(init), which is used for group hopping of Demodulation ReferenceSignal (DM-RS) that is a reference signal for demodulation on the PSSCH,is computed at the second start points, and the following equation isused.

$\begin{matrix}{c_{init} = \left\lfloor \frac{\left( {{SA}\mspace{11mu}{ID}} \right)}{30} \right\rfloor} & \left\lbrack {{Equation}\mspace{14mu} 5} \right\rbrack\end{matrix}$

Equation 5 is derived from the following equation 6 which computes aninitial value c_(init) that is used for group hopping of demodulationreference signal which is a reference signal for the demodulation ofPUSCH, by substituting an identifier SA ID included in a schedulingassignment for an identity (ID) n_(ID) ^(RS) for the reference signal.Computing group hopping of a demodulation reference signal which is areference signal for demodulating PSSCH or PUSCH may be referred to ascomputing DM-RS base sequence.

$\begin{matrix}{c_{init} = \left\lfloor \frac{n_{ID}^{RS}}{30} \right\rfloor} & \left\lbrack {{Equation}\mspace{14mu} 6} \right\rbrack\end{matrix}$

<PD2DSCH Channel>

For PD2DSCH channel, following parameters may be configured.

TABLE 1 Baseband Signal Processing Parameter PD2DSCH configurationScrambling Cell ID PSSID RNTI independent of UE ID (= fixed to 0) Slotnumber independent of the slot number (= fixed to 0) Codeword indexfixed to 0 DMRS base Group hopping Enabled sequence Sequence hoppingDisabled Δshift 0 Cell ID PSSID DMRS CS(cyclic shift) A firstembodiment: 0 A second embodiment: By PSSID bit 1, 2, 3 OCC A firstembodiment: Fixed to [1 1] (orthogonal A second embodiment: By PSSID bit0 cover code)

Referring to Table 1, in the baseband signal processing to generatePD2DSCH, each parameter is configured to comply with PD2DSCH whenscrambling and generating DM-RS base sequence (group hopping) and DM-RS.The processing of the initial value of pseudo-random sequence andbaseband processing is as follows. Here, the PD2DSCH may have the sameformat as that of PUSCH in WAN communication such as LTE, etc.

According to an exemplary embodiment, when a UE attempts to transmitPD2DSCH, an initial value c_(init) is computed at the third starts usedfor scrambling a codeword on the PD2DSCH, and the following equation isused.c _(init)=(PSSID)  [Equation 7]

Equation 7 is derived from the following equation 8 which computes aninitial value c_(init) used for scrambling a codeword on PUSCH, bysetting wireless network temporary identifier n_(RNTI) to 0 regardlessof a UE ID, setting the index of the codeword as q=0, setting slotnumber n_(s) to 0 regardless of D2D slot number, and substituting PSSIDfor a cell ID N_(ID) ^(CELL).c _(init) =n _(RNTI)·2¹⁴ +q·2¹³ +└n _(S)/2┘·2⁹ +N _(ID)^(cell)  [Equation 8]

According to an exemplary embodiment, when a UE attempts to transmitPD2DSCH, an initial value c_(init), which is used for frequency hoppingof resource block assigned for the PD2DSCH transmission, is computed atthe third start points, and the following equation is used.c _(init)≤(PSSID)  [Equation 9]

Equation 9 is derived from the following equation 10 which computes aninitial value c_(init) used in frequency hopping of resource blockassigned for PUSCH transmission, by substituting 0 for SFN n_(f) (incase of TDD), and substituting PSSID for a cell ID N_(ID) ^(CELL).FDD:c_(init)=N_(ID) ^(cell)TDD:c _(init)=2⁹·(n _(f) mod 4)+N _(ID) ^(cell)  [Equation 10]

According to an exemplary embodiment, when a UE attempts to transmitPD2DSCH, an initial value c_(init), which is used for group hopping ofdemodulation reference signal which is a reference signal for thedemodulation of the PD2DSCH, is computed at the third start points, andthe following equation is used.

$\begin{matrix}{c_{init} = \left\lfloor \frac{({PSSID})}{30} \right\rfloor} & \left\lbrack {{Equation}\mspace{14mu} 11} \right\rbrack\end{matrix}$

Equation 11 is derived from the following equation 12 which computes aninitial value c_(init) used for group hopping of demodulation referencesignal which is a reference signal for the demodulation of PUSCH, bysubstituting PSSID for an ID n_(ID) ^(RS) of the reference signal.Computing group hopping of demodulation reference signal which is areference signal for the demodulation of PD2DSCH or PUSCH may be referto as computing DM-RS base sequence.

$\begin{matrix}{c_{init} = \left\lfloor \frac{n_{ID}^{RS}}{30} \right\rfloor} & \left\lbrack {{Equation}\mspace{14mu} 12} \right\rbrack\end{matrix}$

Referring to FIG. 5, based on an initial value c_(init) computed inaccordance with various exemplary embodiments, a UE generatespseudo-random sequence (S505).

Pseudo-random sequence c(i) may be defined by length-31 Gold sequence.c(i) is a binary pseudo-random sequence and may have the value of 0or 1. Output sequence c(n) having length M_(PN) (n=0,1, . . . ,M_(PN)−1)can be defined as shown in equation 13.c(n)=(x ₁(n+N _(C))+x ₂(n+N _(C)))mod 2x ₁(n+31)=(x ₁(n+3)+x ₁(n))mod 2x ₂(n+31)=(x ₂(n+3)+x ₂(n+2)+x ₂(n+1)+x ₂(n))mod 2  [Equation 13]

In equation 13 N_(C)=1600, and a first m-sequence x₁(i) can beinitialized as x₁(0)=1, x₁(n)=0, (n=1, 2, . . . , 30). As describedabove, the initialization of a second m-sequence x₂(i) may result todifferent values, based on system parameters used in a channel or signalto which a pseudo-random sequence is applied as shown in equations 1, 3,5, 7, 9 and 11.

A UE performs, based on a pseudo-random sequence, baseband processing ina subframe (S510). Here, baseband processing may include, for example,scrambling on a codeword of a D2D communication channel, frequencyhopping for resource blocks assigned for D2D communication channeltransmission, and group hopping of demodulation reference signal whichis a reference signal for demodulating D2D communication channel.

As such, by defining an initial value of a pseudo-random sequenceadapted to a D2D communication and start points of computing the initialvalue, a transmitting UE may effectively configure a pseudo-randomsequence for scrambling, frequency hopping, and/or group hoppingdepending on D2D resource configuration.

FIG. 6 is a diagram illustrating an example of a UE to transmit a D2Dcommunication signal through a D2D communication channel, according toone or more exemplary embodiments.

Referring to FIG. 6, a first UE 600, which is a transmitting or sourceUE, transmits to a second UE 650 D2D data channel, discovery signal,PD2DSCH, etc., and the second UE 650, which is a receiving UE, receivesfrom the first UE D2D data channel, discovery signal, PD2DSCH, etc. Theroles of the first UE 600 and the second UE 650 can be exchanged. Forexample, the first UE 600 can be a receiving UE, and the second UE 650can be a transmitting UE or a source UE. Though the detailed componentsand functions of the first UE 600 will be described hereinafter, thesame components and/or functions may be applied to the second UE 650.

The first UE 600 includes a processor 610, a radio frequency (RF) unit620, and a memory 625.

The memory 625 connected to the processor 610, stores variousinformation for operating the processor 610. The RF unit 620 inconnection with the processor 610, transmits and/or receives a wirelesssignal. For example, the RF unit 620 may transmit to the second UE 650PD2DSS, SD2DSS, D2D data channel, discovery signal, PD2DSCH, or receivefrom the second UE 650 PD2DSS, SD2DSS, D2D data channel, discoverysignal, and PD2DSCH.

Further, the processor 610 may include a random sequence processing unit612 and a baseband processing unit 614.

Specifically, the random sequence processing unit 612 computes aninitial value c_(init) to be used for generating pseudo-random sequencec(i), at a determined start point, such as the start of each D2Dsubframe (the first start points), each D2D slot (or at the beginning(or start) of each D2D slot) fulfilling n_(s_D2D)=0 (the second startpoints), and the start of each D2DSS subframe (the third start points),etc.

Here, a random sequence processing unit 612 may compute an initial valuec_(init) based on equation and start defined by the types of a D2Dcommunication channel and a baseband processing in which a correspondingpseudo-random sequence is utilized.

In one or more exemplary embodiments, when the first UE 600 attempts totransmit D2D data via PSSCH which is a D2D communication channel, andthe baseband processing unit 614 carries out scrambling on a codeword onthe PSSCH, the random sequence processing unit 612 computes an initialvalue c_(init) at the first start points and utilizes the followingequation.c _(init)=(SA ID)·2¹⁴ +└n _(S_D2D)/2┘·2⁹+510  [Equation 14]

More specifically, for a physical sidelink processing, the randomsequence processing unit 612 sets 510 instead of a cell ID used forscrambling, sets an identifier SA ID included in scheduling assignmentinstead of RNTI value n_(RNTI) used for the scrambling, and computes aninitial value by setting the index of the codeword to 0. The basebandprocessing unit 614 carries out scrambling of a codeword on the PSSCHbased on the initial value.

In one or more exemplary embodiments, in case where the first UE 600attempts to transmit D2D data on PSSCH which is a D2D communicationchannel and the baseband processing unit 614 carries out frequencyhopping on a resource block assigned for the transmission of PSSCH, therandom sequence processing unit 612 computes an initial c_(init) valueat the second start points, and utilizes the following equation.c_(init)=510  [Equation 15]

More specifically, the random sequence processing unit 612 sets a valueof 510 as an initial value. Then, the baseband processing unit 614performs frequency hopping on a resource block assigned for thetransmission of PSSCH based on the initial value.

In one or more exemplary embodiments, in case where the first UE 600attempts to transmit D2D data on PSSCH which is a D2D communicationchannel and the baseband processing unit 614 carries out group hoppingof a demodulation reference signal which is a reference signal fordemodulating the PSSCH, the random sequence processing unit 612 computesan initial c_(init) value at the second start points, and utilizes thefollowing equation.

$\begin{matrix}{c_{init} = \left\lfloor \frac{\left( {{SA}\mspace{11mu}{ID}} \right)}{30} \right\rfloor} & \left\lbrack {{Equation}\mspace{14mu} 16} \right\rbrack\end{matrix}$

More specifically, the random sequence processing unit 612 computes aninitial value by setting an identifier SA ID included in schedulingassignment instead of a reference signal identifier used for grouphopping. Then, the baseband processing unit 614 performs group hoppingof demodulation reference signal which is a reference signal fordemodulating the PSSCH based on the initial value.

In one or more exemplary embodiments, in case where the first UE 600attempts to transmit PD2DSCH, and the baseband processing unit 614carries out scrambling of a codeword on the PD2DSCH, the random sequenceprocessing unit 612 computes an initial value c_(init) at the thirdstart points, and utilizes the following equation.c _(init)=(PSSID)  [Equation 17]

More specifically, the random sequence processing unit 612 sets PSSID asan initial value, and carries out scrambling of a codeword on PD2DSCHbased on the initial value.

In one or more exemplary embodiments, when the first UE 600 attempts totransmit PD2DSCH, and the baseband processing unit 614 carries outfrequency hopping on a resource block assigned for transmitting thePD2DSCH, the random sequence processing unit 612 computes an initialvalue c_(init) at the third start points, and utilizes the followingequation.c _(init)=(PSSID)  [Equation 18]

More specifically, the random sequence processing unit 612 sets PSSID asan initial value, and the baseband processing unit 614 carries outfrequency hopping on a resource block assigned for the transmission ofPD2DSCH based on the initial value.

In one or more exemplary embodiments, when the first UE 600 attempts totransmit PD2DSCH, and the baseband processing unit 614 carries out grouphopping of a demodulation reference signal which is a reference signalfor demodulating the PD2DSCH, the random sequence processing unit 612computes an initial value c_(init) at the third start points, andutilizes the following equation.

$\begin{matrix}{c_{init} = \left\lfloor \frac{({PSSID})}{30} \right\rfloor} & \left\lbrack {{Equation}\mspace{14mu} 19} \right\rbrack\end{matrix}$

More specifically, the random sequence processing unit 612 sets SA IDthat is an identifier included in scheduling assignment, instead of areference signal identifier used for group hopping, to compute aninitial value, and the baseband processing unit 614 carries out grouphopping of a demodulation reference signal which is a reference signalfor demodulating PD2DSCH based on the initial value.

Further, according to one or more exemplary embodiments, a processor ofa UE may process an initialization for a D2D communication between userequipments (UEs). The processor may determine D2D subframes availablefor a D2D communication. The D2D subframes may be D2D data subframesallocated to transmit D2D data and used for D2D data transmission bymapping D2D data channels therein. The D2D data subframes are includedin a D2D resource pool, and a D2D resource pool may include resourcesfor transceiving control information for a D2D communication andresources for transceiving data for a D2D communication. The D2Dsubframes includes a first D2D subframe and a second D2D subframe. Eachof the first D2D subframe and the second D2D subframe including a D2Dslot corresponding to D2D slot number 0. At the start of the D2D slot ofthe first D2D subframe and at the start of the D2D slot of the secondD2D subframe, the processor may process an initialization associatedwith a pseudo-random sequence of a D2D communication. Each of the firstD2D subframe and the second D2D subframe further includes a D2D slotcorresponding to D2D slot number 1, and at least one of the first D2Dsubframe and the second D2D subframe corresponds to a non-zero subframenumber of a radio frame. For example, as shown at the bottom of FIG. 3,the third subframe in frame 0 has subframe number 2, but has D2D slotnumber 0 and D2D subframe number 0. The eighth subframe in frame N hassubframe number 7, but has D2D slot number 0 and D2D subframe number 0.A radio frequency signal transmitter may transceive a D2D signalassociated with the pseudo-random sequence.

Further, D2D slots in a D2D resource pool may be indexed in an ascendingorder from 0 such that the first D2D slot in the D2D resource pool hasD2D slot number 0. By applying modulo-20 operations for each D2D slot,D2D slot numbers are determined to have one of 0, 1, 2, . . . , 18, and19. An initialization of a pseudo random sequence may be performed atthe start of each D2D slot fulfilling n_(s_D2D)=0 (or e.g., at thebeginning of every D2D slot fulfilling n_(ss) mod 20=0 or n_(ssf) mod10=0). Here, the pseudo random sequence may be associated with thefrequency hopping or the group hopping described herein. When the D2Dsubframe corresponds to the PSSCH subframe used for transmitting a PSSCH(and/or the D2D slot corresponds to a PSSCH slot used for transmitting aPSSCH, an initialization of a pseudo random sequence may be performed atthe start of each D2D slot fulfilling n_(ns) ^(PSSCH) mod 20=0 orn_(ssf) ^(PSSCH) mod 10=0). Here, n_(ss) ^(PSSCH) corresponds to a slotindex of a PSSCH slot and n_(ssf) ^(PSSCH) corresponds to a subframeindex of a PSSCH subframe. More specifically, the D2D subframe may bethe PSSCH subframe for configuring a D2D resource pool including PSSCHsubframes and PSSCH subframes may be indexed in an ascending order andthe PSSCH subframe number n_(ssf) ^(PSSCH) may be determined by themodulo-10 operation. Further, each PSSCH subframe may consist of twoPSSCH slots, and the PSSCH slot number n_(ss) ^(PSSCH) may be determinedfrom the PSSCH subframe number or by applying the modulo-20 operation toindexes of PSSCH slots. In such a configuration, subframes to be used totransmit PSSCH may be determined as D2D subframes and may be indexed andnumbered.

According to one or more exemplary embodiments, each of the D2Dsubframes consists of two D2D slots having consecutive D2D slot numbers.The D2D subframes are included in a resource pool defined in the atleast two radio frames. The at least two radio frames include a firstradio frame and a second radio frame. Each of the first radio frame andthe second radio frame consists of ten subframes, and the first D2Dsubframe may correspond to a subframe of the first radio frame having anon-zero subframe number. The second D2D subframe may correspond to asubframe of the second radio frame having a non-zero subframe number.

The processing the initialization may include initializing at least oneof a first initialization value associated with a frequency hopping fora transmission of a physical sidelink shared channel (PSSCH) and asecond initialization value associated with a group hopping for ademodulation reference signal (DM-RS) to demodulate a PSSCH. Theprocessing the initialization may include initializing a pseudo randomsequence generation associated with the frequency hopping with the firstinitialization value, and initializing a pseudo random sequencegeneration associated with the group hopping with the secondinitialization value. The processor may include a random sequencegenerating unit to generate a pseudo random sequence associated with thefrequency hopping with the first initialization value, and to generate apseudo random sequence associated with the group hopping with the secondinitialization value.

According to one or more exemplary embodiments, at a start of each D2Dsubframe, an initialization value associated with a scrambling of acodeword associated with a transmission of a physical sidelink sharedchannel (PSSCH) may be initialized. Further, at the start of each D2Dsubframe, a scrambling sequence generation with Cinit may beinitialized, where C_(init)=(SA ID)·2¹⁴+n_(sf_D2D)2⁹+510, SA IDcorresponds to an identity associated with a scheduling assignment,n_(sf_D2D) corresponds to a D2D subframe number of the respective D2Dsubframe.

Further, when a frequency hopping for a transmission of a physicalsidelink shared channel (PSSCH) is enabled, an initialization valueassociated with the frequency hopping may be computed at a start of eachD2D slot corresponding to the D2D slot number 0, and the initializationvalue includes a value of 510.

Further, when a group hopping for a demodulation reference signal(DM-RS) associated with a transmission of a physical sidelink sharedchannel (PSSCH) is enabled, an initialization value associated with thegroup hopping may be computed at a start of each D2D slot correspondingto D2D slot number 0, and the initialization value corresponds to

${C_{init} = \left\lfloor \frac{\left( {{SA}\mspace{11mu}{ID}} \right)}{30} \right\rfloor},$where SA ID corresponds to an identity associated with a schedulingassignment.

As shown in FIG. 13, D2D slots corresponding to D2D slot numbers 2 to 19exist between the first D2D subframe and the second D2D subframe in anascending order.

According to one or more exemplary embodiments, a UE may perform:indexing at least one of a D2D slot and a D2D subframe available for aD2D communication, the D2D subframe being included in a radio frame andcomprising the D2D slot, the radio frame comprising at least one non-D2Dsubframe unavailable for a D2D communication; determining at least oneof a D2D slot number associated with the D2D slot and a D2D subframenumber associated with the D2D subframe, based on a modulo operation;and determining an initialization associated with a pseudo-randomsequence of a D2D communication, the initialization being associatedwith the D2D slot or the D2D subframe. The at least one of the D2D slotand the D2D subframe has a non-zero index, and the at least one of theD2D slot number associated with the D2D slot and the D2D subframe numberassociated with the D2D subframe is zero.

As shown in FIG. 3, the radio frame has a system frame number (SFN)associated with an evolved NodeB (eNodeB) or a D2D frame number (DFN)associated with a cluster head UE. The D2D subframe may be associatedwith a Physical Sidelink Shared Channel (PSSCH) through which data of aD2D communication is transmitted between UEs.

With regard to the indexing and a modulo operation, the UE may performdetermining a D2D resource pool comprising the D2D subframes, andindexing the D2D subframes of the D2D resource pool in an ascendingorder. D2D subframe numbers for the indexed D2D subframes aredetermined, based on a modulo-10 operation, and the initializationassociated with a pseudo-random sequence of a D2D communication isperformed at a start of each slot corresponding to D2D slot number 0 orat a start of each subframe corresponding to D2D subframe number 0.

A D2D resource pool including the D2D subframes available fortransmitting data of the D2D communication may be determined in advance.For Time Division Duplex (TDD) system, uplink subframes in the radioframe may correspond to D2D subframes. According to the TDD system,uplink subframes in a radio frame may be determined based on TDD UL-DLconfigurations. Details of the TDD UL-DL configurations are defined in3GPP standards specification, such as “3rd Generation PartnershipProject; Technical Specification Group Radio Access Network; EvolvedUniversal Terrestrial Radio Access (E-UTRA); Physical channels andmodulation (Release 12)”, 3GPP TS36.211 V12.3.0 (September 2014).Details of TDD UL-DL configurations defined in 3GPP TS36.211 V12.3.0 arehereby incorporated by reference, but exemplary embodiments are notlimited thereto. In FDD system, a radio frame (having SFN or DFN)includes ten uplink subframes, and thus the ten uplink subframes in theradio frame may be D2D subframes of a D2D resource pool.

With regard to initialization periods, an initialization value Cinitused for generating the pseudo random sequence c(i) may be obtained at astart of each D2D slot corresponding to D2D slot number 0. Theinitialization value Cinit may correspond to an initial value used for aD2D demodulation reference signal (DM-RS), and the D2D DM-RS may be usedfor demodulating a Physical Sidelink Shared Channel (PSSCH) for a D2Ddata communication.

Further, according to one or more exemplary embodiments, a method of aUE to perform a D2D data communication with another UE in a wirelesscommunication system includes: confirming D2D subframes for a datatransmission of a D2D communication, the D2D subframes being D2D datasubframes for transceiving D2D data and being included in a D2D resourcepool; allocating indexes to D2D slots in the D2D resource pool;allocating D2D slot numbers to the D2D slots by applying a modulooperation to the indexes; and initializing a pseudo random sequence fora D2D communication at each slot with D2D slot number=0. Each D2Dsubframe may consist of two D2D slots. Further, the D2D resource poolmay be defined within at least 4 radio frames, and each radio frame mayconsist of 10 subframes. The applied modulo operation may be modulo-20operation. The D2D subframes may be PSSCH subframes in which PSSCH ismapped to transmit or receive data for a D2D data communication.

The initializing of the pseudo random sequence for a D2D communicationmay include computing an initial value Cinit for generating pseudorandom sequence c(i) at each D2D slot fulfilling n_(ss) ^(PSSCH)=mod20=0 (or at each D2D subframe fulfilling n_(ssf) ^(PSSCH) mod 10=0) inassociation with a DM-RS. The initializing of the pseudo random sequencefor a D2D communication may include, at each D2D slot fulfilling n_(ss)^(PSSCH) mod 20=0, computing an initial value

$C_{init} = \left\lfloor \frac{\left( {{SA}\mspace{11mu}{ID}} \right)}{30} \right\rfloor$associated with a demodulation reference signal (DM-RS) for demodulatinga PSSCH in which D2D data is mapped and initializing a pseudo randomsequence.

The initializing of the pseudo random sequence for a D2D communicationmay include computing an initial value Cinit for generating pseudorandom sequence at each D2D slot fulfilling n_(ss) ^(PSSCH) mod 20=0 (orat each D2D subframe fulfilling n_(ss) ^(PSSCH) mod 10=0) in associationwith a frequency hopping. The initial value may be 510 and may be usedin association with a frequency hopping for allocated resource blocksfor transmitting PSSCH.

A scrambling sequence for a D2D communication may be initializedperiodically and an initial value Cinit associated with the scramblingsequence may be computed at each PSSCH subframe. The initial value Cinitmay be C_(init)=(SA ID)·2¹⁴+n_(sf_D2D)·2⁹+510 and may be used for ascrambling of a codeword, which is transmitted through a PSSCH.

The above description is to explain exemplary embodiments of inventiveconcept, and it will be apparent to those skills in the art thatmodifications and variations can be made without departing from thespirit and scope of inventive concept. Thus, it is intended that thepresent invention cover the modifications and variations of exemplaryembodiments provided they come within the scope of the appended claimsand their equivalents.

What is claimed is:
 1. A method of performing a device-to-device (D2D)communication between user equipments (UEs), the method comprising:discovering between the UEs with a discovery signal transmitted inPhysical Sidelink Discovery Channel (PSDCH); synchronizing between theUEs with a synchronization signal including a primary synchronizingsignal and a secondary synchronizing signal; determining D2D framesavailable for the D2D communication from an available D2D resource pool,wherein each of the D2D frames consists of 10 D2D subframes, and whereineach of the D2D subframes consists of two D2D slots; initializing apseudo-random sequence for the D2D communication with an initializationvalue associated with a group hopping for a demodulation referencesignal (DM-RS) on a physical sidelink shared channel (PSSCH) at a D2Dslot of number 0 in each of the D2D frames; and at a start of each ofthe D2D subframes, initializing an initialization value associated witha scrambling of a codeword associated with a transmission of a PSSCH,wherein the primary synchronizing signal is transmitted in first twoSingle Carrier-FDMA (SC-FDMA) symbols and the secondary synchronizingsignal is transmitted in second two SC-FDMA symbols, wherein the firsttwo SC-FDMA symbols are transmitted in a same D2D subframe and thesecond two SC-FDMA symbols are transmitted in a same D2D subframe. 2.The method of claim 1, further comprising: initializing a frequencyhopping on a physical sidelink shared channel (PSSCH) at a D2D slot ofnumber 0 in each of the D2D frames.
 3. The method of claim 2, whereinthe initialization value associated with the scrambling comprises avalue of
 510. 4. The method of claim 1, wherein the initializing apseudo-random sequence comprising: initializing a pseudo random sequencegeneration associated with the frequency hopping with a firstinitialization value; and initializing a pseudo random sequencegeneration associated with the group hopping with a secondinitialization value.
 5. The method of claim 1, further comprising: atthe start of each of the D2D subframes, initializing a scramblingsequence generation with C_(init), where C_(init)=(SAID)·2¹⁴+n_(sf_D2D)·2⁹+510, SA ID corresponds to an identity associatedwith a scheduling assignment, n_(sf_D2D) corresponds to a number of D2Dsubframe.
 6. The method of claim 1, wherein the group hoppinginitialization value corresponds to${C_{init} = \left\lfloor \frac{\left( {{SA}\mspace{11mu}{ID}} \right)}{30} \right\rfloor},$where SA ID corresponds to an identity associated with a schedulingassignment.
 7. A user equipment (UE) to perform a device-to-device (D2D)communication with another UE, the UE comprising: a processor configuredto discover the another UE with a discovery signal transmitted inPhysical Sidelink Discovery Channel (PSDCH); synchronize with theanother UE with a synchronization signal including a primarysynchronizing signal and a secondary synchronizing signal; determine D2Dframes available for the D2D communication from an available D2Dresource pool, wherein each of the D2D frames consists of 10 D2Dsubframes, and wherein each of the D2D subframes consists of two D2Dslots; initialize a pseudo-random sequence for the D2D communicationwith an initialization value associated with at least one of a grouphopping for a demodulation reference signal (DM-RS) on a physicalsidelink shared channel (PSSCH) at a D2D slot of number 0 in each of theD2D frames; and initialize an initialization value associated with ascrambling of a codeword associated with a transmission of a PSSCH at astart of each of the D2D subframes; and a radio frequency signaltransmitter to transceive a D2D signal associated with the pseudo-randomsequence, wherein the D2D frames are frames in which a PSSCH istransmitted or received, wherein the primary synchronizing signal istransmitted in first two Single Carrier-FDMA (SC-FDMA) symbols and thesecondary synchronizing signal is transmitted in second two SC-FDMAsymbols, wherein the first two SC-FDMA symbols are transmitted in a sameD2D subframe and the second two SC-FDMA symbols are transmitted in asame D2D subframe.
 8. The UE of claim 7, wherein the processor furtherconfigured to initialize a frequency hopping on a physical sidelinkshared channel (PSSCH) at a D2D slot of number 0 in each of the D2Dframes.
 9. The UE of claim 8, wherein the initialization valueassociated with the scrambling comprises a value of
 510. 10. The UE ofclaim 8, wherein the processor further configured to initialize a pseudorandom sequence generation associated with the frequency hopping with afirst initialization value; and initialize a pseudo random sequencegeneration associated with the group hopping with a secondinitialization value.
 11. The UE of claim 7, wherein the processorfurther configured to at the start of each of the D2D subframes,initialize a scrambling sequence generation with C_(init), whereC_(init)=(SA ID)·2¹⁴+n_(sf_D2D)·2⁹+510, SA ID corresponds to an identityassociated with a scheduling assignment, n_(sf_D2D) corresponds to anumber of D2D subframe.
 12. The UE of claim 7, wherein the processoruses a group hopping initialization value corresponds to$C_{init} = \left\lfloor \frac{\left( {{SA}\mspace{11mu}{ID}} \right)}{30} \right\rfloor$for the group hopping for the DMRS, wherein SA ID corresponds to anidentity associated with a scheduling assignment.